Chiari malformation is commonly considered a congenital condition. To our knowledge, reports of progressively symptomatic Chiari Iota malformation with craniometaphyseal dysplasia are rare. The authors present a case of progressively symptomatic Chiari Iota malformation occurring in an 11-month-old infant with craniometaphyseal dysplasia. The patient presented with a typical facial appearance and radiological skeletal survey. Posterior fossa decompression was performed. In the meantime, the patient was given Rocaltrol (calcitriol) and adopted a low calcium diet. His neurological symptoms were markedly improved after surgery. The clinical presentations, radiographical features and prognosis of the patient are discussed with reference to the literature.